Strategies for fertilizer management to achieve higher yields and environmental and fertilizer benefits of rice production in China.

The challenge in China is to retain high yields while lowering greenhouse gas (GHG) emissions in the context of the increasing global and Chinese demand for rice yield. Better fertilizer management is a key factor that favors intensive rice systems toward more intensive, diverse, and sustainable development to obtain higher yield and environmental benefits. Thus, we used a data-intensive approach to estimate yield, fertilizer productivity (FP) and GHG emissions based on fertilizer and soil characteristics across major Chinese rice-producing regions. The common rice production model showed medium yield, low emission intensity and FP, and low or high GHG emissions. Approximate 41 % and 10 %, 34 % and 3 %, 8 % and 2 %, and 8 % and 1 % probabilities for medium and high yield (MY and HY)-low emission intensity (LI)-low GHG emissions (LG)-high FP (HF) (MY-LI-LG-HF and HY-LI-LG-HF) were achieved in Northeast, South, Southwest, Central and East China, respectively, by adjusting basal, tillering and panicle fertilization and soil pH, N, P and K. Our results provide insights for adjusting soil nutrient traits and fertilizer inputs according to regional production potentials for higher yields and FP and lower GHG emissions in China.

Can reduced-input direct seeding improve resource use efficiencies and profitability of hybrid rice in China?

The mechanization of rice production in China has been accompanied by a rapid reduction in agricultural labor forces and increase in machinery purchase subsidies; however, the comprehensive performance of several major mechanized production modes regarding output, environmental protection, and profit remains uncertain to the Chinese government and farmers alike. Here, a five-year (2015-2019) field experiment was conducted to analyze the performance of farmers' mechanized seedling transplanting (FMST), farmers' mechanized direct seeding (FMDS), and reduced-input direct seeding (RIDS) concerning grain yield, energy use, greenhouse gas emissions, and economic benefits. RIDS used an unmanned aerial vehicle for sowing, fertilizing, and spraying, while adopting no-tillage, bed-furrow irrigation technology. The quantity and stability of RIDS-produced grain were similar to those of FMST and higher than those of FMDS. Furthermore, RIDS yields required significantly less machinery, human labor, fuel, and water, with 34.72% and 24.03% decreases in total energy input compared to that for FMST and FMDS, corresponding to 1.45- and 1.34-fold increases in energy productivity, respectively. The resulting CO2-eq emissions from agricultural inputs for RIDS were 71.26% and 71.32% of those for FMST and FMDS, while CH4 emissions were 32.60% and 29.24% of those for FMST and FMDS, respectively. Despite the high N2O emissions and decomposing trend of soil organic carbon in RIDS, the net global warming potential still decreased by 48.84-58.36%, and the carbon sustainability index and carbon efficiency ratio increased by 87.67-142.14% and 105.32-188.22%, respectively, compared with those of FMST and FMDS. RIDS had the lowest cost, its net return was USD 298.81 ha-1 higher than that of FMDS (similar to FMST), and its benefit-cost ratio was 10-36.19% higher than that of FMST and FMDS. Generally, RIDS offered a higher-yielding, cleaner, more sustainable rice production technology for meeting the needs of the Chinese government and farmers.